The Boston Medical Center/Boston University Medical Campus (BMCBUMC) currently does not possess a working fluorescent activated cell sorter (FACS). In this shared instrument grant proposal, we request a state-of-the-art Cytomation MoFlo cell sorter. All of the 15 major users of the FACS currently are funded by the NIH to perform research that involves cell sorting. These users currently use instruments in other institutions across the state of Massachusetts, at great expense in terms of time and money to their research efforts. These busy machines have proven to be insufficient for the needs of BUMC users because BUMC users have low priority and are often excluded from these instruments. Furthermore, the inconvenience of driving off-campus to an outside institution is an inefficient use of investigator time, and is often aggravated by a progressive loss of cell viability, resulting in reduced research quality. The BUMC campus contains many individuals with extensive FACS experience who have agreed to contribute their expertise to insure the effective use of the FACS cell sorter. Dr. Douglas Golenbock, who has been sorting for over 11 years, will direct the day-to-day management of the machine; Dr. Elizabeth Simons (a pioneer in the development of fluorochromes for FACS) has agreed to provide additional expertise. The machine will be integrated into the Maxwell Finland Laboratory FACS Facility, a shared resource that is directed currently by Dr. Golenbock. A management plan, user fees and scheduling, has been fashioned by the FACS Advisory Committee and is ready to be put into place as soon as the instrument is purchased. Institutional support has been guaranteed by the Dean, the Chair of the Department of Medicine, and the Graduate School of Medicine to support the instrument. This includes support for new construction, sufficient funding to cover the expenses of a full-time 100% dedicated FACS cell-sorting technician and funds to help maintain a service contract. Although primarily to be used for BL-2 work, the new FACS facility will be capable of providing an environment for BL-3 ) work one afternoon per week, in order to facilitate experiments with highly pathogenic mycobacteria. The planned intermittent BL-3 level work will have no impact on other investigators, who will work under standard operational lab safety protocols at all other times. No comparable facility currently exists in the City of Boston. We believe that BUMC has the demonstrable need, the on-site technical expertise, a workable management plan and the strong institutional support necessary to qualify for an NIH SIG award.